Flood-fearing parrots commit 'gendercide' for survival

CHOOSING between your children is not a desirable scenario under any condition, but Eclectus parrots do it all the time. When times are tough, they kill their male chicks. Outside human societies, such "gendercide" is rare, but paradoxically it might aid the parrots' survival.

Eclectus roratus lives in Australia and on neighbouring islands. Females make nests in the hollows of trees, where they can flood in heavy rain. When this happens, mothers sometimes kill their male young while allowing the females to live, says Robert Heinsohn of the Australian National University in Canberra, who carried out an eight-year survey of 42 nest hollows. "Evolutionary theory tells us that this behaviour should not happen," he says. An excess of females would struggle to find mates.

Heinsohn believes he knows what drives the parrots to perform selective infanticide. Female offspring have a better chance of surviving during floods because they fledge a week earlier. So from the mother's point of view at least, it makes sense to kill the male and save the energy required to care for it (Current Biology, DOI: 10.1016/j.cub.2011.08.064).

"If you're going to kill your offspring, it's better to do so as soon as possible," says Hope Klug of the University of Tennessee at Chattanooga. Nature has provided a handy twist to the tale: male and female chicks are different shades of grey, making it easier to tell which is which.

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